1. Field of the Invention
The present invention relates generally to magnetic recording heads, and, more particularly, to a compensation system for the fringe field effects induced in very high density, multi-track servo recording heads.
2. Description of the Related Art
A multi-track servo recording head assembly is described in U.S. Pat. No. 5,229,895 for recording a unique servo control track on a magnetic recording tape that can be used to control the track-to-track positioning of a magnetic read/write head during recording and playback of computer data. In this patent, the servo track is created by alternately erasing and not erasing portions of a servo track onto which a servo signal previously had been recorded so as to form a longitudinal series of erase portions along the servo section of the magnetic recording tape. The erase portions of each servo track are used by a head position control system to position a plurality of sets of read/write transducers in the recording head assembly in line with selected data tracks on a data portion of the magnetic recording tape.
Although the multi-track servo track generated by a recording head of the type described in U.S. Pat. No. 5,229,895 allows for an increased number of data tracks to be defined along a magnetic recording tape, it is to be expected that servo control errors will tend to increase as the track density of the magnetic recording tape is increased. For very high density recording at track pitches that are less than 60 .mu.m, and particularly less than 40 .mu.m, variations in servo track position may exceed the tolerance margins of the head position control system, in which case, servo control errors are generated. Accordingly, it would be desirable to provide a system to reduce or prevent the types of servo control errors that may occur in magnetic recording tapes having very high density servo tracks recorded by multi-track servo recording heads.
Although the existence of fringe fields produced by magnetic recording heads is partially known and understood in terms of single head recording assemblies, there has been no indication that fringe fields might cause problems when using a multiple erase head recording assembly to create multi-track recordings that require very uniform track widths. At dimensions less than 60 .mu.m, and particularly less than 40 .mu.m, however, the fringe fields of adjacent erase elements interact so as to create a combined fringe field that is larger than the fringe field of a single erase element when both erase elements are recording the same signal. As a result, the servo track pitch of the region erased by inner erase elements tends to be somewhat larger than the servo track pitch of the region erased by outer erase elements in the servo section. This variation in servo track pitch can cause variations in servo position that ultimately lead to servo control errors when the variations extend beyond the tolerance range of the head positioning control system.